1. The Extraordinary Properties of Water

2. Outline Water is polar Hydrogen bonds
Interaction between water molecules
Water properties:
Cohesion
Adhesion
High specific heat
High heat of vaporization
Less dense as a solid
Density of water
Homeostasis

3. Water is polar
Three models of a water molecule (polar). From left: stick (structural) model, Bohr model, space-filling (cloud) model.

4. Hydrogen Bonds

5. What are the Properties of Water?1

6. Cohesion
Attraction between particles of the same substance ( why water is attracted to itself)
Results in Surface tension (a measure of the strength of water’s surface) 1

7. Helps insects walk across water
Cohesion …
Helps insects walk across water

8. Adhesion Attraction between two different substances.
Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.
Capillary action-water molecules will “tow” each other along when in a thin glass tube.
Examples: transpiration process which plants and trees remove water from the soil, and paper towels soak up water. 1

9. Adhesion and capillary action…

10. High Specific Heat
Amount of heat needed to raise or lower 1g of a substance 1° C.
Water resists temperature change, both for heating and cooling.
Water can absorb or release large amounts of heat energy with little change in actual temperature. 1

11. High Heat of Vaporization
Amount of energy to convert 1g or a substance from a liquid to a gas
In order for water to evaporate, hydrogen bonds must be broken.
As water evaporates, it removes a lot of heat with it (cooling effect) 1

12. 1

13. Heat radiated from the sun warmed surface of the earth is
Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.
Heat radiated from the sun warmed surface of the earth is
absorbed and held
by the vapor. 1

14. Water is Less Dense as a Solid
Ice is less dense as a solid than as a liquid (ice floats)
Liquid water has hydrogen bonds that are constantly being broken and reformed.
Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances. 1

15. Water is Less Dense as a Solid
Which is ice and which is water? 1

16. Water is Less Dense as a Solid
Ice 1

17. Homeostasis
Ability to maintain a steady state despite changing conditions
Water is important to this process because:
a. Makes a good insulator
b. Resists temperature change
c. Universal solvent
d. Coolant
e. Ice protects against temperature extremes (insulates frozen lakes) 4

18. THE END